Do you know what kind of phone cable was run in your house?
I lucked out, turns out they used CAT5 so I was able to have a hub on every floor of my townhouse using the unused pairs of wire (green and brown) for pins 1, 2, 3 and 6. Got some home depot face places and punch down jacks for RJ11 and RJ45, am able to have both the legacy POTS and home networking nice and neat.
Pop the lid off your phone jack and see what type of cableing if your place is relatively new then you may be in luck too.
Another method is ethernet over power adaptors, such as GigaFast "HomePlug" series
worth a look if you don't want to mess with any existing wiring